Help picking a bench power supply

Discussion in 'Power Electronics' started by live4soccer7, Dec 26, 2009.

  1. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    I am in need of a bench power supply. I'm looking for one that will be good for testing stuff such as small lcds, car decks, leds etc.... I would like the ability to have the low end voltage as well as some higher voltages so that it will be a great all around supply. Same goes with the available current. Any suggestions in at least brands of specific ones?
     
  2. Wendy

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    Mar 24, 2008
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  3. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    thanks for the info. I'm not really looking to make a power supply. I just want to purchase a nice adjustable bench power supply. I don't really have the time to make one. I live in that US, the west side of the states.
     
  4. maxpower097

    Well-Known Member

    Feb 20, 2009
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    You can get old HP lab supplies on ebay for $100-$200. You also may want to look at Tattoo gun power supplies, these are usually mass produced and some have decent specs. People have different opinions but with most equipment I prefer old commercial stuff over new hobbiest stuff.
     
  5. someonesdad

    Senior Member

    Jul 7, 2009
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    If you can give more information like:

    1. How much you're willing to spend
    2. Minimum and maximum voltage
    3. Minimum and maximum current
    4. Constant voltage and constant current or just constant voltage?
    5. What type of metering (if any)?
    6. Level of regulation needed
    7. Whether you want a linear supply or a switching supply
    8. Your skill level with electronics
    you'll get more specific recommendations. Now, I know you might not know the answers to all those questions (or what they mean), but the more information you can provide, the more specific the help will be.

    Probably the most important question is how much money you're willing to spend.

    It sounds like you want to buy something, not make something, right?

    Added via edit:

    Went to lunch and didn't see the extra posts after I came back.

    I second the notion of buying used supplies from ebay. 4 of the 6 power supplies I have are older HP bench supplies and they're good stuff. I've had them a number of years and they went in the range of $50-$100. Today, you'll probably pay in the $100-$300 range for these supplies; I think they're still worth it.

    If I were in the market for another supply, I'd stay away from the HP Harrison supplies, as they're getting a bit long in the tooth. The ones made in the mid 80's and beyond are just fine, assuming they're still working. If you're willing to try to troubleshoot them yourself or find a friend to do it for you, you can get some great deals. If you want a working supply, you should look for a seller that offers you a right of return.
     
    Last edited: Dec 26, 2009
  6. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    I'd be willing to spend up to $300 for a nice one.


    1. How much you're willing to spend - up to $300
    2. Minimum and maximum voltage - 0-30v (somewhere around there unless someone thinks there is a good reason to have a larger voltage)
    3. Minimum and maximum current (0-20A, I would like to be able to test things such as small lcds, car decks, and things like leds and circuits)
    4. Constant voltage and constant current or just constant voltage? (I'm not really sure, if someone has some input, that would be great)
    5. What type of metering (if any)? (It would be nice to know the amount of current that is being drawn from the circuit, if that is what you are referring to).
    6. Level of regulation needed (not sure on the answer to that one)
    7. Whether you want a linear supply or a switching supply (not sure how to answer, opinions?)
    8. Your skill level with electronics (I've got some basic circuit building experience and some electronics courses under the belt)
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I paid $79.95 for this one in Dallas.

    [​IMG]

    http://www.vellemanusa.com/us/enu/product/view/?id=522797

    I still haven't used it enough to have an opinion, good or bad. 0 - 15VDC, 0 - 3A

    For the voltage/current specs you may be a bit low on the estimated cost, unless it is used. Could be wrong about that.

    Velleman has other units, of course, that may be more to your liking.
     
  8. PRS

    Well-Known Member

    Aug 24, 2008
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    I got a power supply on ebay for 15 dollars plus 25 dollars shipping. Its in working condition and is good quality. It is variable from zero to 50 volts and good for 150 watts with adjustable current limiting.

    I'm really happy with it. I will never make homemade supplies again when it comes to general purpose needs. Given such a cheap price building my own is no longer necessary.

    But, for a variety of needs I made a bulk supply consisting two independent 25 volt dc units -- each made with a big transformer, macho bridge rectifiers and big capacitors. Whenever I need a dedicated regulated supply I make it in its own box and power it with the bulk supply. This has worked out pretty good for me as I am a chronic experimenter.
     
  9. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    What are some good brands that I could be looking for? I'll take a look at the Vellmans
     
  10. Wendy

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    HP was considered top of the line, they've changed their name though. Don't remember to what.
     
  11. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    Any brands/companies to look at?
     
  12. Wendy

    Moderator

    Mar 24, 2008
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    Post #10???
     
  13. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    Sorry, didn't see it before posting.
     
  14. PIC_User

    Member

    Sep 22, 2008
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    Hewlett-Packard Company is now called Agilent Technologies:eek:

    -Adam-
     
  15. live4soccer7

    Thread Starter Well-Known Member

    Jun 7, 2008
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    Thanks for the info. I'll be sure to look into it. Is there anything I should watch out for when looking for a power supply or any features that come highly recommended?
     
  16. PRS

    Well-Known Member

    Aug 24, 2008
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    Try Lambda power supplies in a search.
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    Hmmm, I prefer constant current instead of current foldback. You can do more with it.
     
  18. someonesdad

    Senior Member

    Jul 7, 2009
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    That's a 600 W supply, which is fairly big for a bench power supply. There's a 400 W (20 V, 20 A) older HP DC supply currently on ebay when I looked earlier today; the buy it now price was $225 if I recall correctly. The shipping was around $90 (this is a full rack width instrument and is pretty heavy). From the looks, I would guess it was probably made around 1980-1985. It would be an excellent supply, but doesn't quite meet your specs. Those designs were linear supplies, which are on the order of 50-60% efficient. More modern switching designs that are smaller are available.

    Take a look at B&K's offerings at http://www.bkprecision.com/products/categories/14/power-supplies.html. You'll see that supplies like you want are in the $1-2k range. This is obviously over your budget. Thus, you'll either have to buy a used supply or drop your specs.

    I have a modern DC power supply made in China that is a nice bench supply with three separate supplies in it and it can supply 180 W total. But these more modern devices don't work quite as nicely as what I consider the standard power supply -- the HP linear supplies from the 1980/1990 time frame. Those things were built like tanks and had very predictable performance, at least in my experience.

    By the way, HP did not change its name to Agilent. HP's Test and Measurement Division was split off from HP as a separate company and took on the name Agilent. The HP that was left kept business like printing and computers.

    Here's a quickie explanation of some of the terms. Constant voltage means you turn a knob to set the voltage to a particular level and the supply does its best to keep that voltage constant in the face of a changing load resistance. Constant current is the analogous behavior for current. The typical lab bench power supply has both constant current and constant voltage capabilities. Personally, I wouldn't consider any other kind, as I use constant current mode even more than constant voltage.

    The metering types you can get are analog meters or digital meters. For most purposes, the analog meters are fine. For measurement work, however, I prefer the digital meters for both current and voltage, as they can obviate the need for external meters.

    Regulation measures how much the output voltage changes when the load changes. For example, my favorite bench supply (an HP E3615A) will change its output voltage less than 0.01% of setting + 2 mV for a full load to no load change in output current. Analogous specs exist for current too.

    Linear and switching refer to the basic technology used in the power supply. Linear has been around longer, but is less efficient. Switching is usually capable of higher power per unit volumes and lower costs. Both are capable technologies.
     
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